Joining method

Abstract

To provide a joining method for joining two objects to be joined to form a cavity, which can efficiently set a state where the inner pressure of the cavity has been reduced to a target inner pressure.SOLUTION: A first joining method stacks a second object to be joined on a first object to be joined under the atmosphere of an atmospheric pressure lower than a prescribed atmospheric pressure, and then annularly forms a fastening part for fastening the second object to the first object along the outer peripheral edge of the first object while maintaining the atmosphere, thereby sealing the inside of the annular form. A second joining method stacks the second object on the first object having a plurality of device regions under the atmosphere of an atmospheric pressure lower than the prescribed atmospheric pressure, and then forms a fastening part for fastening the second object to the first object so as to be annular surrounding the device regions while maintaining the atmosphere, thereby sealing the inside of the annular form.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a bonding technique using a laser beam.

Background Art

[0002] In devices such as MEMS (Micro Electro Mechanical Systems), elements such as sensors (acceleration sensors, gyro sensors, etc.), micro machines (actuators, etc.), and electronic circuits may be sealed in a cavity (see, for example, Patent Document 1). In the manufacturing process of such a device, two bonding targets (a bonding target provided with a recess to be a cavity and a bonding target for closing the recess) are used, and after installing the above elements in the recess, the two bonding targets are bonded to form a cavity and at the same time seal the above elements in the cavity.

[0003] On the other hand, depending on the type of element sealed in the cavity, it is important to keep the internal pressure of the cavity at an appropriate value in order to improve the performance of the element. As an example, when the element is an acceleration sensor, the internal pressure of the cavity is preferably set to an appropriately low value so that air resistance can cause attenuation in the acceleration sensor. As another example, when the element is a gyro sensor, the internal pressure of the cavity is preferably as low as possible (in other words, the degree of vacuum is as high as possible).

[0004] Conventionally, as a method of setting the internal pressure of the cavity to the target internal pressure (an appropriate value according to the element), (1) First, the two bonding targets are aligned in their positional relationship and overlapped, (2) Next, temporary bonding is performed to maintain the adjusted positional relationship, (3) Then, after placing the two bonding targets in the chamber, the internal pressure of the chamber is reduced until it reaches an air pressure approximately the same as the target internal pressure of the cavity, (4) Then, in the chamber, main bonding for sealing the cavity is performed. Such a method was used.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the above-described conventional method, by utilizing the differential pressure generated by reducing the internal pressure of the chamber, the air in the cavity is caused to flow out to the outside through the gap between the joining surfaces (the portion other than the temporarily joined portion) formed when two joining targets are overlapped, thereby attempting to reduce the internal pressure of the cavity to the target internal pressure.

[0007] The inventor has found that in the conventional method, it is difficult to reduce the internal pressure of the cavity to the target internal pressure, or even if it is possible, it takes a significantly long time to reduce it to the target internal pressure. The reason for this is that after overlapping two joining targets, even if a differential pressure is generated, the flow path resistance increases in the gap between the joining surfaces, which makes it difficult to cause the air to flow out to the outside through the gap between the joining surfaces.

[0008] Therefore, an object of the present invention is to efficiently create a state in which the internal pressure of the cavity has been reduced to the target internal pressure in a joining method of joining two joining targets to form a cavity.

Means for Solving the Problems

[0009] The first bonding method according to the present invention includes a stacking step and a fixing portion forming step (Aspect 1). In the stacking step, the second bonding target is stacked on the first bonding target in an atmosphere at a pressure lower than a predetermined pressure. After the stacking step, in the fixing portion forming step, while maintaining the above atmosphere, a fixing portion for fixing the second bonding target to the first bonding target is formed in an annular shape along the outer peripheral edge of the first bonding target, thereby sealing the inside of the annular shape.

[0010] The second bonding method according to the present invention includes a stacking step and a fixing portion forming step (Aspect 2). In the stacking step, the second bonding target is stacked on the first bonding target having a plurality of device regions in an atmosphere at a pressure lower than a predetermined pressure. After the stacking step, in the fixing portion forming step, while maintaining the above atmosphere, a fixing portion for fixing the second bonding target to the first bonding target is formed in an annular shape surrounding the plurality of device regions, thereby sealing the inside of the annular shape.

[0011] In the bonding method according to Aspect 2 above, a recess that becomes a cavity may be formed in each device region of the first bonding target. In the stacking step, as the above atmosphere, an atmosphere in which the pressure is reduced until it becomes the same value as or near the internal pressure target value (the target internal pressure in the cavity after sealing) of the cavity may be used (Aspect 3).

[0012] According to Aspects 1 to 3 above, in the stacking step, by a simple method of overlapping two bonding targets in an atmosphere at a pressure lower than a predetermined pressure, the inside of the cavity before sealing formed there can be made to have the same pressure as the pressure of the atmosphere at that time. Moreover, by simply adjusting the pressure of the atmosphere when performing the stacking step to a pressure comparable to the internal pressure target value of the cavity after sealing, it is possible to reduce the pressure inside the cavity before sealing to a level comparable to the internal pressure target value. Then, in the subsequent fixing portion forming step, by forming the fixing portion in an annular shape while maintaining the above atmosphere and sealing the inside of the annular shape, even when the bonding target is exposed to an atmosphere at a predetermined pressure (such as atmospheric pressure) or an atmosphere at a higher pressure, it is possible to keep the pressure inside the annular shape at the internal pressure target value.

[0013] The third bonding method according to the present invention includes a substitution step, a lamination step, and a fixing portion formation step (Aspect 4). In the substitution step, after evacuating the chamber in which the first bonding target and the second bonding target are arranged, a predetermined gas is injected to replace the atmosphere with the predetermined gas. In the lamination step, the second bonding target is stacked on the first bonding target in an atmosphere filled with the predetermined gas. After the lamination step, in the fixing portion formation step, while maintaining the above atmosphere, a fixing portion for fixing the second bonding target to the first bonding target is formed in an annular shape along the outer peripheral edge of the first bonding target, thereby sealing the inside of the annular shape.

[0014] The fourth bonding method according to the present invention includes a substitution step, a lamination step, and a fixing portion formation step (Aspect 5). In the substitution step, after evacuating the chamber in which the first bonding target having a plurality of device regions and the second bonding target are arranged, a predetermined gas is injected to replace the atmosphere with the predetermined gas. In the lamination step, the second bonding target is stacked on the first bonding target in an atmosphere filled with the predetermined gas. After the lamination step, in the fixing portion formation step, while maintaining the above atmosphere, a fixing portion for fixing the second bonding target to the first bonding target is formed in an annular shape surrounding the plurality of device regions, thereby sealing the inside of the annular shape.

[0015] According to the above-described Aspect 4 or 5, by evacuating the inside of the chamber and then injecting a predetermined gas in the replacement step, it becomes easier to replace the inside of the chamber with an atmosphere mainly composed of the predetermined gas. Then, in the lamination step, by a simple method such as overlapping two joining targets under the atmosphere filled with the predetermined gas in this way, the inside of the cavity before sealing formed there can be filled with the same gas as the atmosphere at that time. Moreover, by simply appropriately selecting the type of gas filling the inside of the chamber, it becomes possible to fill the inside of the cavity before sealing with a desired gas. Then, in the subsequent fixing portion forming step, by forming the fixing portion annularly while maintaining the above-described atmosphere and sealing the inside of the annulus, even when the joining targets are exposed to the air, it becomes possible to keep the inside of the annulus filled with the desired gas.

[0016] In the joining method according to any one of the above-described Aspects 2, 3, and 5, the second joining target may have a device region corresponding to the device region of the first joining target. In the lamination step, alignment of at least one of the positions of the first joining target and the second joining target may be performed so that the positions of the corresponding device regions coincide with each other, and after the alignment, the second joining target may be overlapped on the first joining target (Aspect 6).

[0017] According to the above-described Aspect 6, when wirings, electrodes, etc. are formed in both of the corresponding two device regions, it becomes possible to adjust their positional relationship so that they can be electrically correctly connected at the time of joining.

[0018] The joining method according to any one of the above-described Aspects 1 to 6 may have the following configuration (Aspect 7). The joining method may further include a metal layer forming step of forming a metal layer on at least one of the joining surfaces of the first joining target and the joining surface of the second joining target as a step performed before the lamination step. Then, in the fixing portion forming step, by locally irradiating the metal layer interposed between the first joining target and the second joining target with a laser beam, the irradiated portion of the laser beam may be locally heated to form an annular fixing portion.

[0019] According to the above-described Aspect 7, at the irradiation location of the laser beam (the location where formation of the fixing portion is planned), the metal layer can be melted together with the first joining target and the second joining target, or the metal that is the main component of the metal layer can be diffused into the first joining target and the second joining target. As a result, at each interface between the first joining target and the second joining target and the metal layer, a compound (such as a metal silicide) or an alloy (such as a metal-Si alloy) of the main components (such as a semiconductor) of the first joining target and the second joining target and the metal is formed. In other words, a fixing portion that firmly bonds the first joining target and the second joining target can be formed. Then, by forming such a fixing portion in a circular shape in an atmosphere at a pressure lower than a predetermined pressure, the inside of the circular shape can be reliably sealed while remaining in a state at a pressure lower than the predetermined pressure.

[0020] The fifth joining method according to the present invention includes a temporary joining step and a main joining step (Aspect 8). In the temporary joining step, temporary joining of the first joining target and the second joining target is performed using the joining method according to any one of the above-described Aspects 1 to 7. After the temporary joining step, in the main joining step, the first joining target and the second joining target are further fixed in a region inside the circular fixing portion. At this time, the main joining step is performed using a chamber different from the chamber used for execution of the temporary joining step.

[0021] As described above, in the temporary joining step, a state in which the inside of the cavity (the cavity before sealing) has been reduced to the internal pressure target value is efficiently created. Therefore, in the main joining step, simply by performing joining for sealing the cavity (the cavity before sealing), a cavity (the cavity after sealing) in which the internal pressure is maintained at an appropriate value (the internal pressure target value) can be easily created.

[0022] Also, according to the above-described Aspect 8, since the main joining step is performed using a chamber different from the chamber used for execution of the temporary joining step, it becomes possible to shorten the cycle time required for processing (temporary joining + main joining) of one set of joining targets (the first joining target and the second joining target). Specifically, it is as follows.

[0023] Among the temporary bonding steps, the lamination step (the step that needs to create an atmosphere of lower pressure than a predetermined pressure (for example, an atmosphere with a high degree of vacuum)) and the main bonding step are both processes that require time. Here, if the temporary bonding step and the main bonding step are sequentially performed in one chamber, in that chamber, the next set of bonding targets cannot be processed until the processing of one set of bonding targets is completed. Therefore, the cycle time required for processing one set of bonding targets (temporary bonding + main bonding) becomes long.

[0024] On the other hand, according to the above aspect 8, by performing the main bonding step using a chamber different from the chamber used for executing the temporary bonding step, these steps can be processed in parallel using a plurality of chambers. As a result, it becomes possible to shorten the cycle time required for processing one set of bonding targets (temporary bonding + main bonding).

Effect of the Invention

[0025] According to the present invention, it becomes possible to efficiently create a state where the internal pressure of the cavity has dropped to the target internal pressure.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

[0027] The joining method according to the present invention is a method for joining two joining targets (such as semiconductor wafers; hereinafter referred to as "first joining target W1" and "second joining target W2"). Hereinafter, the embodiments and modifications of the joining method according to the present invention will be specifically described. Note that the joining method described below can be realized using various well-known apparatuses.

[0028] [1] Embodiment In the joining method of the present embodiment, as steps for joining the first joining target W1 and the second joining target W2, two joining steps are sequentially executed roughly. Specifically, as the first joining step, a temporary joining step S1 is performed, and then, as the second joining step, a main joining step S2 is performed. Hereinafter, the details of these joining steps will be described.

[0029] [1-1] Temporary joining step FIGS. 1 and 2 are conceptual diagrams showing the temporary joining step S1 executed in the present embodiment in the order of processing. In the temporary joining step S1, a preparation step S10, a stacking step S11, and an adhering portion formation step S12 are executed in this order.

[0030] [Preparation step S10] In the preparation step S10, a first joining target W1 and a second joining target W2 are prepared. FIGS. 3(A) and (B) are plan views respectively illustrating the first joining target W1 and the second joining target W2 prepared in the preparation step S10. Note that the first joining target W1 and the second joining target W2 shown in FIGS. 1 and 2 show cross-sections along lines A1-A1 and A2-A2 respectively shown in FIGS. 3(A) and 3(B). The same applies to other figures showing various steps.

[0031] In the present embodiment, the first joining target W1 has a plurality of device regions Rd1 that are individualized by cutting along a cutting line Ct (see FIG. 3(A)), and the second joining target W2 has a device region Rd2 corresponding to each device region Rd1 of the first joining target W1 (see FIG. 3(B)). Then, a corresponding pair of device regions Rd1 and Rd2 are cut along the cutting line Ct after joining and individualized, thereby constituting one device.

[0032] Specifically, each device region Rd1 of the first joining target W1 is a portion that forms the base of the device, and a recess 10 serving as a sealed space (cavity) for sealing an element Ge that performs the function of the device is formed in each device region Rd1. Here, the element Ge is a sensor (such as an acceleration sensor or a gyro sensor), a micromachine (such as an actuator), an electronic circuit, or the like. In the present embodiment, the element Ge is an element for which it is important to keep the internal pressure of the cavity at an appropriate value in order to enhance its performance.

[0033] Further, each device region Rd2 of the second joining target W2 is a region that closes the recess 10 of the device region Rd1 of the first joining target W1 corresponding thereto, and is a portion that becomes a lid portion in the device.

[0034] Furthermore, wirings, electrodes, etc. (not shown) that should be connected to each other are formed in the device regions Rd1 and Rd2, and it is required that they be electrically connected correctly during joining.

[0035] <Lamination step S11> In the stacking step S11, using the first joining target W1 and the second joining target W2 prepared in the preparation step S10, the second joining target W2 is stacked on the first joining target W1 in an atmosphere at a pressure lower than the predetermined pressure Pt. Here, the predetermined pressure Pt is the pressure of the atmosphere used in the main joining step S2 described later, and although not particularly limited, for example, it is atmospheric pressure.

[0036] Specifically, first, the first joining target W1 and the second joining target W2 are placed in a chamber 30 capable of adjusting the internal pressure. At this time, the first joining target W1 and the second joining target W2 are arranged in the chamber 30 in a state where their joining surfaces 11s and 21s face each other and are separated from each other (see the upper diagram of S11 shown in FIG. 1). Here, the joining surfaces 11s and 21s are the surfaces that will be joined in the temporary joining step S1 and the main joining step S2, respectively, and are the surfaces where the concave portions 10, wirings, electrodes, etc. connected to each other are exposed.

[0037] Next, by reducing the internal pressure of the chamber 30, an atmosphere is created in the chamber 30 (an atmosphere at a pressure lower than the predetermined pressure Pt) such that the pressure is reduced until it reaches the same value as or near the target internal pressure value Px of the above-described cavity (the sealed space for sealing the element Ge).

[0038] Furthermore, in the present embodiment, in the stacking step S11, alignment of at least one of the positions of the first joining target W1 and the second joining target W2 is performed so that the positions of the corresponding device regions Rd1 and Rd2 coincide with each other. Specifically, by alignment, the positional relationship of wirings, electrodes, etc. formed in the corresponding device regions Rd1 and Rd2 is adjusted so that they can be electrically correctly connected during joining.

[0039] Thereafter, while maintaining the positional relationship after alignment, the second joining target W2 is stacked on the first joining target W1 (see the lower diagram of S11 shown in FIG. 1).

[0040] According to such a lamination step S11, by a simple method of overlapping two joining targets (the first joining target W1 and the second joining target W2) in an atmosphere with a pressure lower than the predetermined pressure Pt, the pressure in the cavity before sealing formed there can be made the same as the pressure of the atmosphere at that time. Moreover, by simply adjusting the pressure of the atmosphere when performing the lamination step S11 to a pressure approximately the same as the target internal pressure value Px of the cavity after sealing, the pressure in the cavity before sealing can be reduced to approximately the same as the internal pressure target value Px. Thereby, it becomes possible to efficiently create a state where the internal pressure of the cavity (here, the cavity before sealing) has dropped to the target internal pressure (the internal pressure target value Px). Thus, according to the lamination step S11, it becomes possible to efficiently control the internal pressure of the cavity before sealing.

[0041] Also, since the positional relationship of wirings, electrodes, etc. formed in the corresponding two device regions Rd1 and Rd2 is adjusted by the above-described alignment, when the second joining target W2 is overlapped on the first joining target W1, they will be electrically correctly connected.

[0042] <Adhesion portion forming step S12> In the adhesion portion forming step S12, while maintaining the atmosphere in the chamber 30 as it is (in other words, at the pressure adjusted in the lamination step S11), an adhesion portion Qs for adhering the second joining target W2 to the first joining target W1 is formed in a ring shape (closed ring shape) along the outer peripheral edge 11t of the first joining target W1, thereby sealing the inside of the ring.

[0043] Specifically, by locally irradiating the interfaces (contact surfaces) of the joint surfaces 11s and 21s with laser light (see the upper diagram of S12 shown in FIG. 2), the irradiated location of the laser light is locally heated to be melted or altered, thereby fixing the joint surfaces 11s and 21s to each other at that local location (see the lower diagram of S12 shown in FIG. 2). At this time, the first joint target W1 and the second joint target W2 may be clamped by a quartz plate or the like so that the degree of adhesion between the joint surfaces 11s and 21s increases. Then, by scanning the laser light along a closed annular pattern (the planned formation pattern Xs of the fixed portion Qs; see FIG. 4), the joint surfaces 11s and 21s are fixed to each other along that pattern. In this way, a closed annular fixed portion Qs is formed.

[0044] FIG. 4 is a plan view illustrating the planned formation pattern Xs of the fixed portion Qs. In the example of FIG. 4, the first joint target W1 is disc-shaped, and the planned formation pattern Xs is set to be annular along the outer peripheral edge 11t at its peripheral edge Re. According to such a shape, the planned formation pattern Xs is set to be annular so as to surround all the device regions Rd1 of the first joint target W1.

[0045] According to such a fixed portion formation step S12, by forming the fixed portion Qs in an annular shape (closed annular shape) while maintaining the atmosphere in the chamber 30 (in other words, while maintaining the air pressure adjusted in the lamination step S11) and sealing the inside of the annulus, even when the first joint target W1 and the second joint target W2 after temporary joining are exposed to an atmosphere of a predetermined air pressure Pt (such as atmospheric pressure) or an atmosphere of a higher air pressure, it becomes possible to keep the air pressure inside the annulus at the internal pressure target value Px.

[0046] [1-2] This joining step FIG. 5 is a conceptual diagram showing the bonding step S2 executed in the present embodiment in the order of processing. In the present embodiment, the first bonding target W1 and the second bonding target W2 after temporary bonding are taken out from the chamber 30, and the bonding step S2 described below is performed on these bonding targets in the atmospheric pressure. Also, in the present embodiment, the bonding step S2 is performed using a chamber different from the chamber 30 used for executing the temporary bonding step S1. Note that these chambers may be constructed within the same single device, or may be constructed in separate devices respectively.

[0047] Here, according to the above-described temporary bonding step S1, the inside of the annular shape of the fixing portion Qs is sealed with an air pressure that is the same as or approximately the same as the internal pressure target value Px. Therefore, by exposing the first bonding target W1 and the second bonding target W2 after temporary bonding to the atmospheric pressure, a pressure difference is generated between the air pressure (internal pressure) inside the annular shape and the air pressure (external pressure) outside the annular shape, and due to this pressure difference, the first bonding target W1 and the second bonding target W2 can be clamped from the back side in the region inside the annular fixing portion Qs. Then, by clamping using such a pressure difference, the bonding surfaces 11s and 21s can be brought into close contact with each other in the region inside the annular fixing portion Qs. The main bonding step S2 is performed in a state where the bonding surfaces 11s and 21s are in close contact with each other in this way.

[0048] And in the main bonding step S2, the first bonding target W1 and the second bonding target W2 are further fixed in the region inside the annular fixing portion Qs formed in the temporary bonding step S1.

[0049] Specifically, for each corresponding device region Rd1 and Rd2 (device regions Rd1 and Rd2 whose positions coincide with each other by alignment), a fixing portion Qt for sealing the cavity (the cavity before sealing) formed in that set of regions is formed. At this time, the fixing portion Qt is formed so as to be an annular shape (a closed annular shape) surrounding the recess 10 constituting each cavity.

[0050] More specifically, by locally irradiating the interfaces (contact surfaces) of the bonding surfaces 11s and 21s in the region inside the fixing portion Qs (see the upper diagram of S2 shown in FIG. 5), the irradiated location of the laser light is locally heated to be melted or altered, thereby fixing the bonding surfaces 11s and 21s to each other at that local location (see the lower diagram of S2 shown in FIG. 5). At this time, the first bonding target W1 and the second bonding target W2 may be clamped by a quartz plate or the like so that the adhesion between the bonding surfaces 11s and 21s is further enhanced. Then, for each corresponding device region Rd1 and Rd2, by scanning the laser light along a closed annular pattern (the planned pattern Xt for forming the fixing portion Qt. See FIG. 6), the bonding surfaces 11s and 21s are fixed to each other along that pattern. In this way, a closed annular fixing portion Qt is formed for each corresponding device region Rd1 and Rd2.

[0051] FIG. 6 is a plan view illustrating the planned pattern Xt for forming the fixing portion Qt. In the example of FIG. 6, the shape of each device region Rd1 is a quadrilateral (and the corresponding device region Rd2 is also a quadrilateral), and in that device region Rd1, the planned pattern Xt is set to be a quadrilateral along the periphery and in an annular shape surrounding the recess 10. Note that the shape of the planned pattern Xt is not limited to a quadrilateral annular shape, and can be appropriately changed to an annular shape of another form (such as a circular shape or a polygonal shape) according to the peripheral shape of each device region Rd1 and the opening shape of the recess 10.

[0052] As described above, in the temporary bonding step S1, a state where the pressure inside the cavity (the cavity before sealing) has decreased to the internal pressure target value Px is efficiently created. Therefore, in this bonding step S2, simply by performing the bonding for sealing the cavity (the cavity before sealing) as described above, a cavity (the cavity after sealing) with the internal pressure maintained at an appropriate value (the internal pressure target value Px) can be easily created.

[0053] Also, in the present embodiment, since the main joining step S2 is performed using a chamber different from the chamber 30 used in the execution of the temporary joining step S1, it is possible to shorten the cycle time required for the processing (temporary joining + main joining) of one set of joining targets (the first joining target W1 and the second joining target W2). Specifically, it is as follows.

[0054] Among the steps of the temporary joining step S1, the lamination step S11 (a step that requires creating an atmosphere at a lower pressure than the predetermined pressure Pt (for example, an atmosphere with a high degree of vacuum)) and the main joining step S2 are both processes that require time. Here, if the temporary joining step S1 and the main joining step S2 are sequentially performed in one chamber, in that chamber, the processing of the next set of joining targets cannot be started until the processing of one set of joining targets is completed. Therefore, the cycle time required for the processing (temporary joining + main joining) of one set of joining targets becomes long.

[0055] On the other hand, according to the manufacturing method of the present embodiment, by performing the main joining step S2 using a chamber different from the chamber 30 used in the execution of the temporary joining step S1, those steps can be processed in parallel using a plurality of chambers. As a result, it becomes possible to shorten the cycle time required for the processing (temporary joining + main joining) of one set of joining targets.

[0056] [2] Modification [2-1] First modification The planned pattern Xs for forming the fixing portion Qs used in the temporary joining step S1 may be appropriately changed to another annular shape as long as it is annular and can surround a plurality of device regions Rd1, and is not limited to the shape (annular along the outer peripheral edge 11t) illustrated in FIG. 4.

[0057] FIGS. 7(A) and 7(B) are plan views showing two examples of the planned pattern Xs for forming the fixing portion Qs used in the first modification. FIGS. 8(A) and 8(B) are plan views showing two other examples of the planned pattern Xs for forming the fixing portion Qs used in the first modification.

[0058] In FIG. 7(A), the pattern Xs to be formed is set to be an annular shape that surrounds all the device regions Rd1 of the first joining target W1 along their outermost edges.

[0059] On the other hand, in FIGS. 7(B) to 8(B), a plurality of device regions Rd1 are divided into several groups, and the pattern Xs to be formed is set to be an annular shape that surrounds all the device regions Rd1 within each group for each group. And in FIG. 7(B), the pattern Xs to be formed is set to be an independent annular shape for each group. In contrast, in FIGS. 8(A) and 8(B), the pattern Xs to be formed is set by combining a circular pattern Xs1 and a linear pattern Xs2 so that a part of the annular shape can be shared between groups. Specifically, it is as follows.

[0060] In FIG. 8(A), the pattern Xs to be formed is composed of a circular pattern Xs1 set annularly along the outer peripheral edge 11t and one linear pattern Xs2 that crosses the inside of the circular pattern Xs1. In this case, the portion of the linear pattern Xs2 in the pattern Xs to be formed is shared between groups, and as a result, the pattern Xs to be formed includes two semi-circular annular shapes that can surround all the device regions Rd1 within each group for each group.

[0061] In FIG. 8(B), the pattern Xs to be formed is composed of a circular pattern Xs1 set annularly along the outer peripheral edge 11t and two linear patterns Xs2 that cross each other (orthogonal in the example of FIG. 8(B)) while crossing the inside of the circular pattern Xs1. Also in this case, the portion of the linear pattern Xs2 in the pattern Xs to be formed is shared between groups, and as a result, the pattern Xs to be formed includes four fan-shaped annular shapes that can surround all the device regions Rd1 within each group for each group.

[0062] [2-2] Second modified example FIG. 9 and FIG. 10 are conceptual diagrams showing the temporary bonding step S1 executed in the second modification example in the order of processing. Further, FIG. 11 is a conceptual diagram showing the main bonding step S2 executed in the second modification example in the order of processing.

[0063] As shown in FIG. 9, in the preparation step S10, a metal layer Lm may be formed on at least one of the bonding surfaces 11s of the first bonding target W1 and the bonding surface 21s of the second bonding target W2 (metal layer forming step). In the example of FIG. 9, a case is shown where the metal layer Lm is formed only at the formation locations of the fixing portions Qs and Qt (see FIGS. 10 and 11) on the bonding surface 21s on the second bonding target W2 side. More specifically, the metal layer Lm is formed at a location that avoids electrodes, wirings, etc. that are electrically connected when the first bonding target W1 and the second bonding target W2 are bonded (a location where the metal layer Lm can be formed in a state of being electrically non-contact with electrodes, wirings, etc.).

[0064] Although not particularly limited, the metal layer Lm is formed with a thickness of 1 μm or less using a film forming method such as vapor deposition. Also, as the main component of the metal layer Lm, metals such as Cu, Al, Cr, Ti, Ta, and Au can be used.

[0065] Note that the metal layer Lm may be formed on the bonding surface 11s on the first bonding target W1 side. Also, the metal layer Lm may be formed on both the bonding surfaces 11s and 21s. In that case, two types of metal layers Lm with different main components may be formed on the bonding surfaces 11s and 21s. When it is not necessary to electrically connect electrodes, wirings, etc. when the first bonding target W1 and the second bonding target W2 are bonded, the metal layer Lm may be formed over the entire surface of at least one of the bonding surfaces 11s and 21s.

[0066] And in this modification example, this metal layer Lm is used for the formation of the fixing portions Qs and Qt in the fixing portion forming step S12 (see FIG. 10) and the main bonding step S2 (see FIG. 11). Specifically, by locally irradiating the laser light to the metal layer Lm intervening between the first bonding target W1 and the second bonding target W2, the irradiated location of the laser light is locally heated to form the annular fixing portions Qs and Qt.

[0067] More specifically, according to the irradiation of the laser beam on such a metal layer Lm (see the upper diagrams of S12 and S2 respectively shown in FIGS. 10 and 11), at the irradiated location of the laser beam (the locations where the fixing portions Qs and Qt are planned to be formed. The planned formation patterns Xs and Xt), the metal layer Lm can be melted together with the first joining target W1 and the second joining target W2, or the metal that is the main component of the metal layer Lm can be diffused into the first joining target W1 and the second joining target W2. As a result, at each interface between the first joining target W1 and the second joining target W2 and the metal layer Lm, a compound (such as a metal silicide) or an alloy (such as a metal-Si alloy) of the main components (such as a semiconductor) of the first joining target W1 and the second joining target W2 and the metal is formed. In other words, the fixing portions Qs and Qt that firmly bond the first joining target W1 and the second joining target W2 can be formed (see the lower diagrams of S12 and S2 respectively shown in FIGS. 10 and 11).

[0068] And in the temporary joining step S1, by forming such a fixing portion Qs in an annular (closed annular) shape in an atmosphere at a pressure lower than the predetermined pressure Pt, the inside of the annular can be surely sealed while maintaining a pressure lower than the predetermined pressure Pt.

[0069] [2-3] Third Modification This joining step S2 is not limited to being executed at atmospheric pressure, and may be performed in an atmosphere pressurized in the chamber. According to such a configuration, the pressure difference between the pressure (internal pressure) inside the annular and the pressure (external pressure) outside the annular can be expanded. As a result, in the region inside the annular fixing portion Qs, the first joining target W1 and the second joining target W2 can be clamped with a greater force. Thereby, even if there is distortion in the first joining target W1 or the second joining target W2, it becomes possible to correct the distortion and bring the joining surfaces 11s and 21s into close contact with each other.

[0070] [2-4] Fourth Modification The above-described bonding method can be applied not only to bonding two objects to be bonded (first object to be bonded W1 and second object to be bonded W2) for the purpose of forming a cavity, but also to bonding two objects to be bonded in various other applications. Also in this case, by utilizing the pressure difference between the air pressure (internal pressure) inside the ring and the air pressure (external pressure) outside the ring, it becomes possible to bring the first object to be bonded W1 and the second object to be bonded W2 into close contact. Further, by performing this bonding step S2 using a chamber different from the chamber 30 used for executing the temporary bonding step S1, it becomes possible to shorten the cycle time required for processing one set of objects to be bonded (temporary bonding + main bonding).

[0071] Furthermore, the above-described bonding method can also be applied to bonding two objects to be bonded for which device regions Rd1 and Rd2 are not set. Also in this case, it becomes possible to bring the two objects to be bonded into close contact and to shorten the cycle time.

[0072] [2-5] Fifth Modification Example In the bonding method of the above-described embodiment, in order to efficiently create a state in which the internal pressure of the cavity has dropped to the target internal pressure (internal pressure target value Px), in the lamination step S11, a process of overlapping two objects to be bonded (first object to be bonded W1 and second object to be bonded W2) was performed in an atmosphere of a lower air pressure than a predetermined air pressure Pt. Instead of this, in this modification example, in order to efficiently create a state in which the cavity is filled with a desired gas (mainly an inert gas such as nitrogen gas, neon gas, argon gas, etc.), the following process is performed in the temporary bonding step S1.

[0073] In the temporary bonding step S1 of this modification example, after performing the same preparation step S10 as in the above-described embodiment, a replacement step S31, a lamination step S32, and a fixing portion formation step S33 are executed in this order.

[0074] <Replacement Step S31> In the replacement step S31, first, the first bonding target W1 and the second bonding target W2 are placed in the chamber 30 capable of injecting gas and adjusting the internal pressure. At this time, the first bonding target W1 and the second bonding target W2 are arranged in the chamber 30 in a state where their bonding surfaces 11s and 21s face each other and are separated from each other (see the upper diagram of S11 shown in FIG. 1).

[0075] Next, by reducing the internal pressure of the chamber 30, the inside of the chamber 30 is evacuated (the state where the atmospheric pressure is reduced to a desired degree of vacuum). Then, by injecting a gas of the same type as the desired gas (mainly an inert gas such as nitrogen gas, neon gas, argon gas, etc.) for filling the cavity into the chamber 30, the inside of the chamber 30 is replaced with an atmosphere filled with the predetermined gas. The internal pressure of the chamber 30 at this time can be adjusted and may be adjusted to a negative pressure lower than the atmospheric pressure or may be adjusted to a positive pressure higher than the atmospheric pressure.

[0076] According to such a replacement step S31, by evacuating the inside of the chamber 30 and then injecting the predetermined gas, it becomes easier to replace the inside of the chamber 30 with an atmosphere mainly composed of the predetermined gas.

[0077] <Lamination step S32> In the lamination step S32, the second bonding target W2 is stacked on the first bonding target W1 in an atmosphere filled with the predetermined gas. Further, similar to the above-described embodiment, at least one of the first bonding target W1 and the second bonding target W2 is aligned so that the positions of the corresponding device regions Rd1 and Rd2 coincide with each other. Then, while maintaining the positional relationship after alignment, the second bonding target W2 is stacked on the first bonding target W1 (see the lower diagram of S11 shown in FIG. 1).

[0078] Here, conventionally, as a method of filling the cavity with the desired gas, (1) First, the two bonding targets are aligned in their positional relationship and overlapped, (2) Next, temporary bonding is performed to maintain the adjusted positional relationship, (3) Then, after placing two objects to be joined into the chamber, the inside of the chamber is evacuated, and (4) then, the inside of the chamber is filled with a gas of the same kind as the desired gas (predetermined gas), (5) Finally, permanent bonding for sealing the cavity is performed inside the chamber. Such a method was used.

[0079] In this conventional method, by evacuating the inside of the chamber in (3), the differential pressure generated at that time (the state where the internal pressure is greater than the external pressure) is utilized to cause the air inside the cavity to flow out to the outside through the gap between the bonding surfaces of the two objects to be joined (the portion other than the temporarily bonded part), thereby attempting to evacuate the inside of the cavity as well. However, as described above, after overlapping the two objects to be joined, even if a differential pressure is generated, the flow path resistance becomes large in the gap between the bonding surfaces, and for this reason, it is considered difficult to let the air flow out to the outside through the gap between the bonding surfaces.

[0080] Also, by filling the inside of the chamber with the predetermined gas in (4), the differential pressure generated at that time (the state where the external pressure is greater than the internal pressure) is utilized to cause the gas inside the chamber to flow into the inside through the gap between the bonding surfaces of the two objects to be joined (the portion other than the temporarily bonded part), thereby attempting to fill the inside of the cavity with the predetermined gas. However, also in this case, due to the large flow path resistance in the gap between the bonding surfaces, it is considered difficult to let the gas flow into the inside through the gap between the bonding surfaces.

[0081] In contrast, according to the lamination step S32 of this modified example, in an atmosphere filled with a predetermined gas, by a simple method of overlapping two objects to be joined (the first object to be joined W1 and the second object to be joined W2), the cavity before sealing formed there can be filled with the same gas as the atmosphere at that time. Moreover, by simply appropriately selecting the type of gas filling the chamber 30, it becomes possible to fill the cavity before sealing with a desired gas. As a result, it becomes possible to efficiently create a state in which the cavity (here, the cavity before sealing) is filled with the desired gas. Thus, according to the lamination step S32, it becomes possible to efficiently control the internal state of the cavity before sealing.

[0082] <Fixing portion forming step S33> In the fixing portion forming step S33, while maintaining the atmosphere in the chamber 30 as it is (in other words, while maintaining the atmosphere filled with a predetermined gas), in the same manner as in the above embodiment, a fixing portion Qs for fixing the second object to be joined W2 to the first object to be joined W1 is formed in an annular shape (closed annular shape) along the outer peripheral edge 11t of the first object to be joined W1, thereby sealing the inside of the annulus (see the lower diagram of S12 shown in FIG. 2, FIG. 4).

[0083] According to such a fixing portion forming step S33, by forming the fixing portion Qs in an annular shape (closed annular shape) and sealing the inside of the annulus while maintaining the atmosphere in the chamber 30 (in other words, while maintaining the atmosphere filled with a predetermined gas), even when the first object to be joined W1 and the second object to be joined W2 after temporary joining are exposed to the air, it becomes possible to keep the inside of the annulus filled with the desired gas.

[0084] Note that the configurations of the first to fourth modified examples described above can also be applied to this modified example.

[0085] [2-6] Other modified examples The metal layer forming step, which is a part of the preparation step S10, may be performed in the chamber 30 where the lamination step S11 is performed.

[0086] When there is no need to shorten the cycle time or when there is a high need to complete the processing (temporary bonding + main bonding) within one chamber, the main bonding step S2 may be performed within the same chamber as the chamber 30 used for the execution of the temporary bonding step S1.

[0087] When wiring, electrodes, etc. to be connected during bonding are not formed on the bonding targets, or when the device regions Rd1 and Rd2 are not set, etc., in cases where high accuracy is not required for the positional relationship between the two bonding targets during bonding, the above-described bonding method may be appropriately modified to perform bonding without alignment in the lamination step S11.

[0088] The descriptions of the above embodiments and modifications should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated not by the above embodiments or modifications, but by the claims. Furthermore, it is intended that the scope of the present invention includes all changes within the meaning and scope equivalent to the claims.

[0089] Also, from the above embodiments and modifications, some steps constituting the bonding method may be partially extracted as the subject of the invention, or each step may be individually extracted. For example, the temporary bonding step S1 and the main bonding step S2 may be individually extracted as the subject of the invention.

Explanation of Reference Numerals

[0090] 10 Concave portion 11s, 21s Bonding surface 11t Outer peripheral edge 30 Chamber Ct Cutting line Ge Element Lm Metal layer Pt Predetermined pressure Px Internal pressure target value Rd1, Rd2 Device region Qs, Qt Fixing portion Re Peripheral portion W1 First bonding target Second joining target of W2 Patterns Xs and Xt to be formed Circular pattern of Xs1 Linear pattern of Xs2 Temporary joining step of S1 Main joining step of S2 Preparation step of S10 Lamination step of S11 Fixing part formation step of S12 Replacement step of S31 Lamination step of S32 Fixing part formation step of S33

Claims

1. A stacking step of stacking a second bonding target on a first bonding target in an atmosphere of a pressure lower than a predetermined pressure; After the stacking step, while maintaining the atmosphere, a fixing portion for fixing the second bonding target to the first bonding target is formed in an annular shape along the outer peripheral edge of the first bonding target, thereby sealing the inside of the annulus. A fixing portion forming step; A bonding method comprising:

2. A stacking step of stacking a second bonding target on a first bonding target having a plurality of device regions in an atmosphere of a pressure lower than a predetermined pressure; After the stacking step, while maintaining the atmosphere, a fixing portion for fixing the second bonding target to the first bonding target is formed in an annular shape surrounding the plurality of device regions, thereby sealing the inside of the annulus. A fixing portion forming step; A bonding method comprising:

3. In each device region of the first bonding target, a recess serving as a cavity is formed; In the stacking step, as the atmosphere, an atmosphere in which the pressure is reduced until it reaches the same value as or near the internal pressure target value of the cavity is used. The bonding method according to claim 2.

4. A replacement step of evacuating the chamber in which the first bonding target and the second bonding target are disposed and then injecting a predetermined gas to replace it with an atmosphere filled with the predetermined gas; A stacking step of stacking the second bonding target on the first bonding target in an atmosphere filled with the predetermined gas; After the stacking step, while maintaining the atmosphere filled with the predetermined gas, a fixing portion for fixing the second bonding target to the first bonding target is formed in an annular shape along the outer peripheral edge of the first bonding target, thereby sealing the inside of the annulus. A fixing portion forming step; A bonding method comprising:

5. A replacement step of evacuating the chamber in which a first bonding target having a plurality of device regions and a second bonding target are disposed and then injecting a predetermined gas to replace it with an atmosphere filled with the predetermined gas; A stacking step of stacking the second bonding target on the first bonding target in an atmosphere filled with the predetermined gas; After the stacking step, while maintaining the atmosphere filled with the predetermined gas, a fixing portion for fixing the second bonding target to the first bonding target is formed in an annular shape surrounding the plurality of device regions, thereby sealing the inside of the annulus. A fixing portion forming step; A bonding method comprising:

6. The second object to be joined has a device region corresponding to the device region of the first object to be joined, In the stacking step, alignment of at least one of the positions of the first object to be joined and the second object to be joined is performed so that the positions of the corresponding device regions coincide with each other, and after the alignment, the second object to be joined is stacked on the first object to be joined. The joining method according to any one of claims 2, 3, and 5.

7. A metal layer forming step of forming a metal layer on at least one of the joining surfaces of the first object to be joined and the second object to be joined before the stacking step, further comprising, In the fixing portion forming step, by locally irradiating the metal layer interposed between the first object to be joined and the second object to be joined with a laser beam, the irradiated portion of the laser beam is locally heated to form the annular fixing portion. The joining method according to any one of claims 1 to 5.

8. A temporary joining step of temporarily joining a first object to be joined and a second object to be joined using the joining method according to any one of claims 1 to 5, After the temporary joining step, a main joining step of further fixing the first object to be joined and the second object to be joined in a region inside the annular fixing portion, comprising, and performing the main joining step using a chamber different from the chamber used for executing the temporary joining step. A joining method.

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